Fibrous sheets are used for cleansing human skin, e.g., skin around anus, or cleaning a toilet room. The fibrous sheet is preferably water-disintegratable to be thrown away and drained in a toilet as it is. If it is not excellent in water-disintegratability, it requires a long time to be dispersed in a septic tank, and brings danger of clogging drainpipes of a toilet, when being thrown away and drained in a toilet. However, in general, a packed fibrous sheet impregnated with a cleansing liquid or the like has to be strong enough to endure conducting wiping operations while being impregnated with a cleansing liquid, and at the same time, has to keep water-disintegratability in the event of being thrown away and drained in a toilet. Therefore, a water-disintegratable fibrous sheet that has good water-disintegratability and strength sufficient to use is demanded.
Unexamined Published Japanese Patent Application No. 1-168999 discloses an easily water-dispersible cleaning product containing water-insoluble carboxymethylated pulp in a salt form of calcium. However, when a large amount of water-insoluble carboxymethylated pulp is used to improve strength, water-disintegratability is deteriorated.
Unexamined Published Japanese Patent Application No 2-229295 discloses a water-disintegratable paper containing a water-soluble binder having a carboxyl group and a metal. Examined Published Japanese Patent Application No. 7-24636 discloses a water-disintegratable cleaning product containing a water-soluble binder having a carboxyl group, a metallic ion and an organic solvent. However, this water-soluble binder cannot be mixed with fibers in water in a production process because of water-solubility thereof, so that the water-soluble binder has to be added to a fibrous sheet after paper manufacturing by means of spraying or the like and the production process is complicated disadvantageously.
Unexamined Published Japanese Patent Applications No. 9-132896 and No. 9-132897 each discloses a water-disintegratable sheet, in which sodium carbonate is added to water-insoluble or water-swellable carboxymethyl cellulose. However, this water-disintegratable sheet is insufficient in water-disintegratability.